Synthesis of pteridines



Patented Apr. 3, 195 1 UNITED STATES orricr.

' srn'rrresrs or PTERIDINES James H. Boothe, Pearl River, N. Y.,assignor to American Cyanamid Company,

New York,

N. Y., a corporation of Maine No Drawing. Application July 27, 1946,Serial No. 686,716

1 This invention relates to a new method of preparing pteroylglutamicacid and related com- .pounds.

N -oH.NH -Nimeoooncngomooon prises, essentially, the step of mixingtogether a 2-amino-4-hydroxy-6- (halomethyl) pteridine,

13 Claims. (8]. 260-251.5)

free amino acid amide. chance of side reactions.

Inasmuch as the Z-aminol-hydroxy-S-(halomethyl) pteridines appear to benew compounds, a description of the preparation of the bromo and chloroderivatives will be given in the specific examples below.

Obviously, in place of the preferred paraaininobenzoylglutamic acid Imay use paraaminobenzoic acid itself or a salt, ester, or amide thereof.The preferred amides are those of the amino acids, such as,specificallmpara-aminm benzoylaspartic acid or para aminobenzoylglycineor amides of amino acids having one or more peptid linkages, such aspara-amino- There is, also, less benzoylglutamylglutamic acid.

with para-aminobenzoic acid, or a salt, ester,

oramide of para-aminobenzoic acid, such as, preferably,para-aminobenzoyl glutamic acid.

The reaction is carried out by heating the reactants at a temperaturepreferably within the range 80 C. to 150 C. while dissolved or suspendedin a solvent. Because of the ease with which the halogen substituent ishydrolyzed oiT it is preferred that the solvent be a non-aqueous liquidsuch as one of the alcohols or alkylene glycols or other inert liquid inwhich the reactants are reasonably soluble.

It is also preferred, but not necessary, that the para-aminobenzoylglutamic acid be added in the form of one of its esters,. such as thediethyl ester. This procedure is desirable in that the esters are moresoluble in the preferred solvents and appear to be more reactive thanthe To illustrate the invention with greater particularity, reference ismade to the following specific examples in which the preferred product,pteroylglutamic acid, is prepared. It will be understood, of course,that these examples are merely illustrative of the process and are notto be construed as limiting the invention to the specific conditions orreactants shown. All parts are by weight unless otherwise indicated.

7 Example 1 200 parts of Z-aminol-hydroxy-G-methyl .pteridine, preparedby the process described in the copending application of John M. Mowat,Serial No. 633,870, filed December 8, 1945, now U. S. Patent 2,443,078,issued June 8, 1948, was mixed with 260 parts of bromine and heated in asealed tube at 100 C. for 5 hours. was then cooled, opened, and the2-amino-4-hydroxy-6(bromomethyl) pteridine was dried over KOH in avacuum for 5 hours. This brominated product consisted of a mixture of6-(m0noand cli-bromomethyl) pteridines with some decomposition product.

The crude brominated product was mixed with 13 parts of dry ethyleneglycol and 1 part of diethyl para-aminobenzoyl glutamate and heated for1 hour at 100-110 C. The reaction mixture was then diluted with 24 partsof ethyl alcohol and the insoluble material separated, washed withalcohol and ether and dried. The product is the diethyl ester ofpteroylglutamic acid.

The ester groups of the above product are very easily removed byhydrolysis; for example, by standing overnight at room temperature in a0.1 N NaOH solution. The product, as obtained, is pteroylglutamic acid,which, upon further purification, may be employed as a therapeutic agentfor conditions in which folic acid or L. casei fac- The tube tor areindicated as useful. A suitable purification procedure is described inthe Science article referred to above.

Example 2 2 parts of 2-amino-4-hydroxy-6-methyl pteridine was sealed ina tube with 2.5 parts of bromine and heated to 150-155 C. for 5 hours.The contents of the tube were dried over KOH for 24 hours in a vacuum.The product was then mixed with 110 parts of ethylene glycol and partsof diethyl para-aminobenzoylglutamate and the solution heated at 100-110C. for 1 hour. The reaction product was then diluted with 240 parts ofethyl alcohol, the mixture centrifuged and the insoluble productrecovered and dried. After hydrolysis of the ester groups the crudeproduct was further purified and found to be identical withpteroylglutamic acid by biological activity, ultra-violet and infra-redabsorption spectra and crystallography tests.

Example 3 5 parts of 2-amino-4-hydroxy-6-methyl pteridine was refluxedwith 167 parts of sulfuryl chloride in a small amount of benzoylperoxide catalyst for 5 hours. The sulfuryl chloride was evaporated offand 1 part of diethyl para-aminobenzoyl glutamate in 11 parts ofethylene glycol was added to the crude 2-amino-4-hydroxy-6-(chloromethyl) pteridine and the mixture heated for 1 hour at 100-ll0 C.The mixture was diluted with alcohol and the product was recovered anddried as in the preceding examples. After hydrolysis of the estergroups, the crude product was examined and found to containpteroylglutamic acid.

Example 4 12 grams of 2-amino-4-hydroxy-6-methyl pteridine was mixedwith 500 cc. 48% hydrobromic acid and 12 cc. bromine was added. Thismixture was heated on a steam bath under reflux'for five hours whennearly all of the starting compound was in solution. After standingovernight the solution was concentrated in vacuo until all the excessbromine was removed. The solution was Norited, filtered and concentratedto about 30 cc. 2.5 liters of cold water was added and the productfiltered out and dried.

4 grams of the above described crude bromomethyl pteridine was heated ona steam bath for three hours with 16 g. diethyl p-aminobenzoylglutamatein 300 cc. ethylene glycol. It was cooled and diluted with 1.2 liters ofacetone. The precipitate was centrifuged and washed with acetone andether and dried. It contained pteroylglutamic acid by chemical assay.

Example 5 100 mg. of the above described crude bromomethyl pteridine washeated one hour on a steam bath with 200 mg. p-aminobenzoylglutamic acidin 6 cc. ethylene glycol. It was cooled and diluted with 24 cc. acetoneand the product centrifuged, washed with acetone and ether, and dried.It contained 7.2% pteroylglutamic acid by chemical assay.

I claim:

1. A method of preparing pteridines which comprises mixing together andheating within the range C. to 150 C. a 2-amino-4-hydroxy-6- halomethylpyrimido [4,5-b] pyrazine with a member of the group consisting ofpara-aminobenzoic acid and its salts, esters and amides thereof andthereafter recovering the pteridine formed.

2. A method of preparing pteridines which comprises mixing together in asolvent and heating the mixture within the range C. to C. a2-amino-4-hydroxy-6-bromomethyl pyrimido [4,5-b] pyrazine with a memberof the group consisting of para-aminobenzoic acid and its salts, estersand amides thereof and thereafter recovering the pteridine formed.

3. A method of preparing pteridines which comprises mixing together in asubstantially anhydrous hydroxylated solvent and heating the mixturewithin the range 80 C. to 150 C. a 2- amino-l-hydroxy-6-halomethylpyrimido [4,5-b] pyrazine with a member of the group consisting ofpara-aminobenzoic acid and its salts, esters and amides thereof andthereafter recovering the pteridine formed.

4. A method of preparing pteridines which comprises mixing together in asubstantially anhydrous hydroxylated solvent a2-amino-4-hydroxy-fi-halomethyl pyrimido [4,5-b] pyrazine with a memberof the group consisting of paraaminobenzoic acid and its salts, estersand amides thereof and heating at a temperature within the range 80 C.to 150 C. and thereafter recovering the pteridine formed.

5. A method of preparing pteridines which comprises mixing together in asolvent and heating the mixture within the range 80 C. to 150 C. a2-amino-4-hydroxy-fi-halomethyl pyrimido [4,5-b] pyrazine with an aminoacid amide of para-aminobenzoic acid and thereafter recovering thepteridine formed.

6. A method of preparing pteroylglutamic acid which comprises mixingtogether in a solvent and heating the mixture within the range 80 C. to150 C. a 2-amino-4-hydroxy-6-halomethyl pyrimido [4,5-b] pyrazine withpara-aminobenzoylglutamic acid and thereafter recovering pteroylglutamicacid.

'7. A method of preparing pteroylglutamic acid which comprises mixingtogether in a solvent and heating the mixture within the range 80 C. to150 C. a 2-amino-4-hydroxy-6-halomethyl pyrimido [4,5-b] pyrazine withthe diethyl ester of para-aminobenzoylglutamic acid and thereafterrecovering pteroylglutamic acid.

8. A method of preparing pteroylglutamic acid which comprises mixingtogether in an inert solvent and heating within the range 80 C. to 150C. 2-amino-4-hydoxy-6-bromomethyl pyrimido [4,5-b] pyrazine and thediethyl ester of paraaminobenzoylglutamic acid and thereafter recoveringpteroylglutamic acid.

9. A method of preparing pteroylglutamic acid which comprises mixingtogether in an inert solvent and heating within the range 80 C. to 150para-ammobenzoylglutamic acid and thereafter recovering pteroyiglutamicacid.

12. A method of preparing pteridines which comprises mixing together ina solvent Z-amino- 4-hydroxy-6-ha1omethy1 pyrimido (4,5-b) pyrazine withan amino acid amide of para-aminobenzoic acid and recovering thepteridine formed.

13. A method of preparing pteroyl-glutamic acid which comprises mixingtogether in a, solvent 2-amino-4-hydroxy-6-ha1omethy1 pyrimido (4,5-b)pyrazine with para-aminobenzoylglutamic acid and recoveringsteroylglutamic acid.

JAMES H. BOOTHE.

No references cited.

1. A METHOD OF PREPARING PTERIDINES WHICH COMPRISES MIXING TOGETHER ANDHEATING WITHIN THE RANGE 80* C. TO 150* C. A2-AMINO-4-HYDROXY-6HALOMETHYL PYRIMIDO (4,5-B) PYRAZINE WITH A MEMBER OFTHE GROUP CONSISTING OF PARA-AMINOBENZOIC ACID AND ITS SALTS, ESTERS ANDAMIDES THEREOF AND THEREAFTER RECOVERING THE PTERIDINE FORMED.